|PPI(4)||Device Drivers Manual||PPI(4)|
ppi — user-space
interface to ppbus parallel 'geek' port
Minor numbering: unit numbers correspond directly to ppbus numbers.
ppi driver provides a convenient means
for user applications to manipulate the state of the parallel port, enabling
easy low-speed I/O operations without the security problems inherent with
the use of the /dev/io interface.
All I/O on the
ppi interface is performed
calls. Each command takes a single uint8_t argument,
transferring one byte of data. The following commands are available:
- Get and set the contents of the data register.
- Get and set the contents of the status register.
- Get and set the contents of the control register. The following defines correspond to bits in this register. Setting a bit in the control register drives the corresponding output low.
- Get and set the contents of the EPP control register.
- Get and set the contents of the ECP control register.
- Read and write the ECP FIFO (8-bit operations only).
To present the value 0x5a to the data port, drive STROBE low and then high again, the following code fragment can be used:
int fd; uint8_t val; val = 0x5a; ioctl(fd, PPISDATA, &val); ioctl(fd, PPIGCTRL, &val); val |= STROBE; ioctl(fd, PPISCTRL, &val); val &= ~STROBE; ioctl(fd, PPISCTRL, &val);
The inverse sense of signals is confusing.
ioctl() interface is slow, and there
is no way (yet) to chain multiple operations together.
The headers required for user applications are not installed as part of the standard system.
|January 2, 1998||Debian|